This invention relates, in general, to high frequency semiconductor integrated circuits, and more particularly, to methods and structures for integrating passive components, logic devices, and electro-static discharge (ESD) devices into a high frequency power transistor process flow.
High frequency power amplifiers are well known and used, for example, in personal communication applications such as cellular telephones and pagers. As the personal communications industry is pushed towards smaller and lighter products, the components that make up these products must also become smaller and lighter. Typical silicon-based high frequency power amplifier circuits for personal communication products are manufactured using discrete components in hybrid integrated circuit configurations. That is, discrete power transistors, resistors, inductors, capacitors, logic devices, and ESD films or devices are formed or placed onto a hybrid circuit board to provide a power amplifier circuit. These hybrid configurations are very expensive and are large in size, with sizes of 2.0 centimeters by 3.0 centimeters being typical.
Silicon-based high frequency devices such as the laterally diffused metal-oxide semiconductor (LDMOS) power transistor are attractive because they provide good performance at frequencies in a range from 100 MHz to about 2 GHz. Also, LDMOS power transistors are more cost effective than III-V based high frequency devices in this frequency range. An example of a high frequency LDMOS power transistor design is provided in U.S. Pat. No. 5,155,563 issued to Robert B. Davies et al. and assigned to Motorola Inc.
High frequency monolithic integrated III-V power amplifier circuits are often used in personal communication applications. However, these devices require a negative power supply because they use depletion mode MESFET power devices. Also, III-V power amplifier circuits have been found to have long term reliability problems. In addition, III-V power amplifier circuits use complex air bridge inductor designs that are difficult to manufacture.
With the drive towards smaller and lighter components in support of smaller and lighter personal communication products, structures and methods are needed that provide for a cost effective and reliable monolithic integration of passive components (e.g., capacitors, inductors, transmission lines, and resistors), ESD components, and logic components into a high frequency power transistor structure.